1. Technical Field
The present invention relates to a liquid ejecting head that ejects liquid by driving of a piezoelectric element and a liquid ejecting apparatus including the same.
2. Related Art
A liquid ejecting apparatus is an apparatus including a liquid ejecting head and ejects various types of liquid from the ejecting head. As a liquid ejecting apparatus, for example, there is an image recording apparatus such as an ink jet type printer or an ink jet type plotter and recently, image recording apparatuses have become applicable to various manufacturing apparatuses by utilizing features that can accurately land a small amount of the liquid at a predetermined position. For example, an image recording apparatus is applicable as a display manufacturing apparatus for manufacturing a color filter of a liquid crystal display and the like, an electrode forming apparatus for forming an electrode of an organic Electro Luminescence (EL) display or a field emission display (FED), and the like, and a chip manufacturing apparatus for manufacturing bio-chips (biological and chemical elements). Then, a liquid ink is ejected from the recording head of the image recording apparatus and a solution for each color of Red (R), Green (G), and Blue (B) is ejected from a color material ejecting head of the display manufacturing apparatus. Furthermore, a liquid electrode material is ejected from an electrode material ejecting head for the electrode forming apparatus and solution of a bio-organic material is ejected from a bio organic material ejecting head for the chip manufacturing apparatus.
The liquid ejecting head described above is configured such that, the liquid is introduced into a pressure chamber, pressure variation is generated in the liquid of the pressure chamber, and the liquid is ejected from nozzles leading to the pressure chamber. As a pressure generation unit that generates the pressure variation in the liquid inside the pressure chamber, a piezoelectric element is preferably used. For example, the piezoelectric element is configured such that a lower electrode film that functions as an individual electrode provided for each pressure chamber, a piezoelectric body layer of lead zirconate titanate (PZT) and the like, and an upper electrode film that functions as a common electrode common to a plurality of pressure chambers are respectively laminated and formed by a film forming technology in order from a side close to the pressure chamber (for example, JP-A-2009-172878). In such a piezoelectric element, a width of the piezoelectric body layer is formed wider than a width of the lower electrode film so that the piezoelectric body layer covers the lower electrode film in a region corresponding to the pressure chamber. Then, a portion sandwiched between the upper and lower electrode films in the piezoelectric body layer is an active section that is deformed by applying a voltage to the electrode films. Such a piezoelectric element is formed on a vibration plate defining one side (for example, opposite side to a nozzle plate in which the nozzles are formed) of the pressure chamber. The vibration plate has flexibility and is deformed depending on the deformation of the piezoelectric element.
Here, as an indicator for performance evaluation of the liquid ejecting head, there is a so-called excluded volume. The excluded volume means a change amount (a volume of liquid excluded from the pressure chamber) of the volume of the pressure chamber when the piezoelectric element is driven by applying a predetermined drive voltage. The excluded volume increases or decreases depending on an area of the active section of the piezoelectric element that is laminated in a region corresponding to the pressure chamber. Thus, it is possible to efficiently eject the liquid from the nozzles by improving the excluded volume.
However, in order to increase an area of the active section of the piezoelectric element, if a width (dimension in a nozzle column direction) of the lower electrode film (individual electrode) is increased, the excluded volume may be reduced. Specifically, since the piezoelectric body layer is configured so as to cover the lower electrode film for suppressing insulation breakdown between the upper electrode film and the lower electrode film, the width of the piezoelectric body layer is also increased along with the width of the lower electrode film being increased. Thus, the width of the piezoelectric body layer is relatively increased with respect to the width of the pressure chamber (opening of a space that is the pressure chamber on the piezoelectric element side) and a width of a region in which the piezoelectric body layer is not laminated is relatively decreased in the region corresponding to the pressure chamber. As a result, deformation of the vibration plate is inhibited in the region and the excluded volume is reduced.